Liquid fuel injection pumps



Jan. 20, 1970 M. DROBI LIQUID FUEL INJECTION PUMPS 2 Sheets-Sheet 1 Filed Feb. 6, 1968 TOR svmswww AT'EQQNEW Jan. 20, 1970 M. DRbBl 3,490,375

4 LIQUID FUEL INJECTION PUMPS Filed Feb. 6, 1968 Y 2 Sheets-Sheet 2 United States Patent US. Cl. 103-2 1 Claim ABSTRACT OF THE DISCLOSURE A liquid fuel injection pump including a plunger movable inwardly by the action of a cam which bears against a roller carried by a roller shoe. The surface of the roller shoe which is presented to the plunger is radiused about an axis which is parallel to the axis of the roller and on the opposite side thereof from said end surface in order to reduce wear on said surface.

Background of the invention This invention relates to liquid fuel injection pumps of the kind comprising in combination, a body part, a driving shaft journalled within the body part, a rotary member mounted within the body part, means coupling the rotary member to the driving shaft, a plunger reciprocably mounted in a radial bore in the rotary member, a cup shaped member mounted on or formed integrally with the driving shaft, the skirt portion of said member extending around said rotary member, a. radial slot defined in said skirt portion coincident with said plunger, a roller shoe slidable within said slot, and a roller carried thereby, the roller projecting beyond the periphery of said skirt, and an annular cam ring surrounding said skirt, with said cam ring having inwardly directed cam lobes whereby to impart inward movement to the roller, the roller shoe and the plunger as the driving shaft is rotated.

Such a pump is described and claimed in the specification of our British Patent No. 972,214. This pump has proved to be very successful but it has been found that appreciable wear of the roller shoe takes place at its point of contact with the plunger and the object of the present invention is to provide such a pump in a form in which the aforesaid wear is minimized.

Summary of the invention According to the invention in a pump of the kind specified the end surface of the roller shoe which is presented to the plunger is radiused about an axis parallel to that of the roller and positioned on the opposite side of the roller to said end surface, the end surface of the plunger being substantially flat.

Brief description of the drawings In the accompanying drawings:

FIGURE 1 is a sectional side view illustrating one example of a pump to which the invention may be applied,

FIGURE 2 is a sectional plan view with parts removed, of the pump of FIGURE 1,

FIGURE 3 is a section through the rotor of the pump of FIGURE 1, and

FIGURE 4 is a portion of FIGURE 3 to an enlarged scale showing the modification in accordance with the invention.

Referring to FIGURES 1, 2 and 3 of the accompanying drawings, there is provided a body 2 within which is rotatably mounted a distributor 3. At one end, the distributor 3 has formed integrally therewith a rotor 4 of an injection pump, with the rotor being of similar diameter to the distributor except at its end, where it is of 3,490,375 Patented Jan. 20, 1970 slightly reduced cross-section. Within the rotor is a diametrical bore within which are contained a pair of plungers 5.

Adjacent to and coaxial with the rotor is a driving shaft 6 adapted to be driven by the engine through gearing 7, 8. The end of the shaft '6 is supported by a hollow housing 2a secured to the body 2, and is formed with an integral cup-shaped extension 6a of greater diameter than the remainder of the shaft. Within the base of the extension 611 is a slot which is engaged by a tongue 4a on the rotor, so that the shaft 6 serves to rotate the rotor 4 and distributor 3. The cylindrical wall portion of the extension is located around the rotor 4, and has formed therein a pair of apertures formed as extensions of said slot and in register with the opposite ends of the bore in the rotor. Slidably mounted in these apertures for radial movement relative to the rotor 4 are a pair of roller shoes 9 having flat surfaces against which the plungers 5 bear. Moreover, the shoes 9 carry a pair of rollers 10 respectively which are adapted to make contact with cam lobes formed on a surrounding annular cam 11 as the distributor rotates, with the cam 11 being secured to the housing 2. The wall portion is arranged to bear against the end of the body 2, so that any longitudinal thrust imparted to the driving shaft 6 by the engine is borne by the body 2. Moreover, the reduction in diameter of the end of the rotor 4 permits slight tilting of the driving shaft 6 while impairing the operation of the pump, and a shoulder 12 between the extension 6a and the remainder of the driving shaft 6 is conveniently employed to secure in position a centrifugal governor 13.

At the opposite end of the distributor 3 is a feed pump 14 of the vaned rotor type, and the feed pump rotor is integral with but of greater diameter than the distributor 3 and is slotted to accommodate the vanes. Moreover, passages 15, 16 are formed in the body and distributor respectively whereby the feed pump can feed fuel to the bore in the rotor 4 in a known manner to move the plungers 5 outwardly, whereafter inward movements are imparted to the plungers by the cam 11 to cause fuel to be delivered in turn to ports 17 in the body adapted for connection to the engine cylinders respectively. The quantity of fuel delivered is determined by a throttle 18 in the passage 15. The throttle 18 is controlled by the governor 13 through linkage and spring means in a manner well known per se but not shown.

In order to minimize the wear on the end faces of the roller shoes 9 which co-operate with the plungers, the aforesaid end faces are radiused about axes which are disposed on the opposite sides respectively of the rollers to said end surfaces and extending parallel to the axes of the rollers. The end surfaces of the plungers are fiat and the radius point is indicated at 20 in FIGURE 4. However, in practice and in one example, the roller diameter is 9.5 mm. whereas the radius is mm. In a pump employing these dimensions no wear of the end face was apparent whereas under identical running conditions with a shoe having a substantially flat surface appreciable wear occurred.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A liquid fuel injection pump for a multi-cylinder internal combustion engine, comprising a hollow body having a plurality of ports adapted for connection respectively to the engine cylinders, a rotary distributor mounted in the hollow body, a rotor rigidly united coaxially with one end of the distributor, said rotor having a transverse bore, at least one plunger slidably positioned in the transverse bore, an annular cam ring surrounding the rotor, said cam ring having inwardly directed cam lobes for imparting inward movements to the plunger during rotation of the rotor and the distributor, a driving shaft adjacent to and coaxial with the rotor, cooperating components on the rotor and driving shaft, engageable to impart rotation of the'driving shaft to the rotor and the distributor, said hollow body and distributor being provided with passages whereby, during rotation of the rotor and the distributor, liquid fuel under pressure can be fed to the transverse bore for moving the plunger outwardly towards the lobes of the cam ring, and can be subsequently discharged through the ports in turn by inward movements imparted to the plunger by the lobes of the cam ring, a cup-shaped extension integral with the end of the driving shaft adjacent the rotor, said extension having a cylindrical wall portion located between the rotor and the cam ring and provided with at least one radial aperture in alignment with the transverse bore, a roller shoe slidably mounted in the radial aperture and a roller carried thereby, said shoe having an end surface bearing against an adjacent end of the plunger so that the plunger causes the roller to contact the lobes of the cam ring during rotation of the rotor and the distributor irrespective of any relative angular displacement of the driving shaft and rotor, said adjacent end of the plunger being flat, and said end surface of the shoe being radiused about an axis parallel to that of the roller and positioned on the opposite side of the roller to the end surface whereby Wear on the end surface of the shoe is minimized.

References Cited UNITED STATES PATENTS WILLIAM L. FREEH, Primary Examiner US. Cl. X.R. l03160 

